Torque determining allen screw

ABSTRACT

The screw has a tool-receiving recess comprising a basically cylindrical outer recessed portion and a hexagonal inner recessed portion. The outer recessed portion has a plurality of nubs or protrusions spaced circumferentially around its cylindrical wall. A conventional hexagonal allen wrench inserted in the outer recessed portion is used to tighten the screw by engagement with the nubs. The nubs are designed so that they will be sheared by the wrench when a predetermined torque is exerted by the wrench. The screw can be loosened by the wrench when the wrench is received in the inner recessed portion. In one embodiment, the wrench can be inserted in the inner recessed portion before the nubs are sheared; in a second embodiment, shearing of the nubs is necessary before the wrench can be inserted in the inner recessed portion.

nite States Patent '[193 Stanback Feb. 11, 1975 TORQUE DETERMINING ALLEN SCREW [75] Inventor: Harris I. Stanback, Lexington, Ky. [73] Assignee: Square D Company, Park Ridge, Ill. [22] Filed: July 30, 1973 [2|] Appl. No.: 384,165

684,82l 12/1952 Great Britain ..85/45 Primary E.\'aminerRamon S. Britts Arturney, Agent, or FirmErnest S. Kettleson; Harold J. Rathbun; Carmen B. Patti [57] ABSTRACT The screw has a tool-receiving recess comprising 21 basically cylindrical outer recessed portion and a hexagonal inner recessed portion. The outer recessed portion has a plurality of nubs or protrusions spaced circumferentially around its cylindrical wall. A conventional hexagonal allen wrench inserted in the outer recessed portion is used to tighten the screw by engagement with the nubs. The nubs are designed so that they will be sheared by the wrench when a predetermined torque is exerted by the wrench. The screw can be loosened by the wrench when the wrench is received in the inner recessed portion. In one embodiment, the wrench can be inserted in the inner recessed portion before the nubs are sheared; in a second embodiment, shearing of the nubs is necessary before the wrench can be inserted in the inner recessed portion.

9 Claims, 6 Drawing Figures Torque indicating wrenches are conventionally used to apply a predetermined torque when tightening a screw having a wrench-receiving socket such as an allen screw. These wrenches are relatively expensive and are not always available. Further, it is of course impossible'to visually examine an installed conventional socket head screw and determine whether it has been tightened to a specified torque. Consequently, a need exists for a socket head screw which can be tightened to a predetermined torque value with a conventional socket wrench and which provides a visible indication that it has been tightened to the predetermined torque value.

SUMMARY OF THE INVENTION This invention provides an improved socket head screw which can be tightened to a known torque value with a conventional socket wrench. A socket head screw in accordance with this invention has a recess extending from one end comprising an outer basically cylindrical recess and an inner wrench-receiving socket. A plurality of inwardly protruding nubs are circumferentially spaced around the cylindrical wall of the outer recess.

When a socket head wrench having a maximum head width slightly less than the diameter of the cylindrical recess is inserted into the cylindrical recess and rotated, surfaces of the wrench adjacent its vertices engage the nubs and turn the screw to advance it inwardly of a threaded opening. The nubs are designed to be sheared when a predetermined torque adequate for tightening the screw to thedesired degree of tightness is applied to them by the wrench, thus providing an indication that the screw has been adequately tightened. The wrench may be inserted into the inner recess to loosen the screw.

The invention is described as applied to an allen head screw which has a hexagonal recess, but its application to other socket head screws is readily apparent.

In one embodiment, the wrench can be fully inserted into the recess before the nubs are sheared. In another embodiment, the nubs are positioned directly above the vertices of the inner hexagonal recess thus blocking entry of the wrench into the inner recess before the nubs are sheared.

It is an object of the invention to provide an improved allen screw which can be tightened to a known torque value using a conventional allen wrench and which provides a visual indication that the known torque value has been reached.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a pair of identical allen screws in accordance with this invention in association with an electrical connector;

FIG. 2 is a top view of one of the allen screws of FIG.

FIG. 3 is a sectional view taken along the lines 3-3 of FIG. 2;

FIGS. 4 and 5 of sectional views taken along the lines 4-4 and 5-5 respectively, of FIG. 3; and

FIG. 6 is a sectional view taken at the same relative location as FIG. 4 showing another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the FIGS. 1 5, a torque determining allen head screw 10 in accordance with one embodiment of the invention is shown. In FIG. 1 a pair of the screws 10 are shown as used to clamp a cable 9 in an electrical connector 11.

The screw 10 has an externally threaded body portion 12 having a recess 14 extending axially from one end, the recess 14 comprising an outer basically cylindrical recess 16 and an adjacent coaxial inner hexagonal recess 18. The cylindrical side wall of the recess 16 is provided with a plurality of circumferentially spaced nubs 20 each generally triangular in cross-section and protruding inwardly from the wall. Each of the nubs 20 has side walls 20a and 20b. As shown, there are preferably three such nubs 20 and, the nubs 20 extend axially inwardly from the head end surface of the screw 10 to the inner end of the recess 16. The nubs 20 may be made shorter if desired to reduce the torque value required for shearing.

The nubs 20 are positioned respectively over alternate ones of a plurality of vertices 22 of the hexagonal recess 18, vertices 23 of the respective nubs 20 being slightly displaced from the vertices 22 immediately beneath them. Shoulders 24 defined at the intersection of the cylindrical recess 16 with the hexagonal recess 18 serve as a support for the head of an allen wrench 30 during initial use of the screw 10.

In use, the hexagonal head of an allen wrench 30 having a maximum width slightly less than the diameter of the cylindrical upper recessl6 is inserted into the recess 16 with end surfaces of the wrench 30 near the vertices of the wrench 30 resting respectively on the guide surfaces 24. The wrench 30 is then rotated clockwise within the cylindrical recess 16 until areas of three of the side walls of the wrenchrespectively engage the side walls 20a of the nubs 20. Further rotation of the wrench 30 causes the screw 10 to rotate clockwise and advance inwardly of an associated threaded member such as a connector of the type shown in FIG. 1. The screw advances until the screw encountersresistance such as contact with a cable as shown inFIG. 1. At this point, the nubs 20 resist further movement of the wrench 30. Increased torque applied to the wrench 30 causes the nubs 20 to shear off thereby insuring that the screw 10 has been tightened to a predetermined torque value.

The screw 10 can be loosened by inserting the wrench 30 into the inner recess 18 and rotating the wrench 30 counterclockwise.

In another embodiment of the invention shown in FIG. 6, an allen screw 32 has an externally threaded portion 34 and a recess 36 extending inwardly from one end surface of the screw 32 and comprising an outer generally cylindrical recess 38 and an inner hexagonal recess 40. A plurality of shearable nubs 42 like the nubs 20 of the first embodiment extend inwardly from the cylindrical side wall of the recess 38, but have their vertices positioned directly above vertices 44 of the hexagonal recess 40 instead of displaced therefrom as in the first embodiment. Therefore, the wrench 30 cannot be advanced into the hexagonal recess 40 until the nubs 42 are sheared and the screw thereby installed at the predetermined torque value.

In either embodiment, the shearing of the nubs 20 or 42 provides a visual indication that the screw or 32 has been installed at a predetermined level of torque.

The screw 10, in the first embodiment is shown as having right-handed threads. The first embodiment of the invention can also be used on a screw with left-hand threads by displacing the nubs slightly to the opposite side of the vertices 22. The second embodiment may be used as shown on a screw with either right-hand or left-hand threads. I

Thus it is apparent that there has been provided, in accordance with the invention, a torque determining tend axially inwardly from said one end face of the screw to an inner end of the cylindrical recess portion.

allen head screw that fully satisfies the objects, aims,

and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

I claim:

1. A torque-determining socket head screw comprising an exteriorly threaded cylindrical body having a tool-receiving recess extending axially thereinto from one end face of the body, the recess having an outer basically cylindrical recess portion defining a cylindrical wall open to an adjacent coaxial inner recess portion having a plurality of angularly disposed flat sides, the inner recess portion having a transverse dimension smaller than the diameter of the outer recess and being designed to receive a standard size tool having angularly disposed sides so as to be complementary to the inner recess, and at least one frangible nub projecting radially inwardly from the cylindrical wall of the outer recess, the nub being engageable by the tool and shearable upon the application of a predetermined torque thereto by the tool thereby providing an indication that the screw when received in a threaded opening has been tightened to a predetermined torque value.

2. A screw as claimed in claim 1 wherein there are additional nubs on the cylindrical wall, the nubs being circumferentially spaced from each other.

3. A screw as claimed in claim 2 wherein the nubs are generally triangular in radial cross-section.

4. A screw as claimed in claim 2 wherein the nubs ex- 5. A screw as claimed in claim 2 wherein the inner recess portion has a plurality of vertices and, the nubs are displaced slightly circumferentially in the same direction from alternate ones of the vertices, respectively.

6. A screw as claimed in claim 2 wherein the inner recess portion has a plurality of vertices and the nubs are in substantial axial alignment with alternate ones of the vertices, respectively, said nubs extending radially inwardly beyond the vertices of the inner recess, thereby requiring shearing of the nubs before the tool can be advanced into the inner recess.

7. A torque determining allen head screw comprising an exteriorly threaded cylindrical body having a toolreceiving recess extending axially thereinto from one end face of the body, the recess having an outer basically cylindrical recess portion defining a cylindrical wall open to an adjacent coaxial inner hexagonal recess portion, the hexagonal recess having a transverse demension smaller than the diameter of the outer recess, the hexagonal recess portion being designed to receive a standard tool such as an allen wrench, and three frangible nubs circumferentially spaced on and projecting radially inwardly from the cylindrical wall of the outer recess, the nubs being engageable by an allen wrench and shearable upon the application of a predetermined torque thereto by the wrench thereby providing an indication that the screw when received in a threaded opening has been tightened to a predetermined torque value.

8. A screw as claimed in claim 7 wherein the inner hexagonal recess portion has six vertices and the nubs are displaced slightly circumferentially in the same direction from alternate ones of the vertices, respectively.

9. A screw as claimed in claim 7 wherein the inner hexagonal recess portion has six vertices and the nubs are positioned in substantial axial alignment with alternate ones of the vertices, said nubs extending radially inwardly beyond the vertices of the inner recess, thereby requiring shearing of the nubs before the wrench can be advanced into the hexagonal recess. 

1. A torque-determining socket head screw comprising an exteriorly threaded cylindrical body having a tool-receiving recess extending axially thereinto from one end face of the body, the recess having an outer basically cylindrical recess portion defining a cylindrical wall open to an adjacent coaxial inner recess portion having a plurality of angularly disposed flat sides, the inner recess portion having a transverse dimension smaller than the diameter of the outer recess and being designed to receive a standard size tool having angularly disposed sides so as to be complementary to the inner recess, and at least one frangible nub projecting radially inwardly from the cylindrical wall of the outer recess, the nub being engageable by the tool and shearable upon the application of a predetermined torque thereto by the tool thereby providing an indication that the screw when received in a threaded opening has been tightened to a predetermined torque value.
 2. A screw as claimed in claim 1 wherein there are additional nubs on the cylindrical wall, the nubs being circumferentially spaced from each other.
 3. A screw as claimed in claim 2 wherein the nubs are generally triangular in radial cross-section.
 4. A screw as claimed in claim 2 wherein the nubs extend axially inwardly from said one end face of the screw to an inner end of the cylindrical recess portion.
 5. A screw as claimed in claim 2 wherein the inner recess portion has a plurality of vertices and, the nubs are displaced slightly circumferentially in the same direction from alternate ones of the vertices, respectively.
 6. A screw as claimed in claim 2 wherein the inner recess portion has a plurality of vertices and the nubs are in substantial axial alignment with alternate ones of the vertices, respectively, said nubs extending radially inwardly beyond the vertices of the inner recess, thereby requiring shearing of the nubs before the tool can be advanced into the inner recess.
 7. A torque determining allen head screw comprising an exteriorly threaded cylindrical body having a tool-receiving recess extending axially thereinto from one end face of the body, the recess having an outer basically cylindrical recess portion defining a cylindrical wall open to an adjacent coaxial inner hexagonal recess portion, the hexagonal recess having a transverse demension smaller than the diameter of the outer recess, the hexagonal recess portion being designed to receive a standard tool such as an allen wrench, and three frangible nubs circumferentially spaced on and projecting radially inwardly from the cylindrical wall of the outer recess, the nubs being engageable by an allen wrench and shearable upon the application of a predetermined torque thereto by the wrench thereby providing an indication that the screw when received in a threaded opening has been tightened to a predetermined torque value.
 8. A screw as claimed in claim 7 wherein the inner hexagonal recess portion has six vertices and the nubs are displaced slightly circumferentially in the same direction from alternate ones of the vertices, respectively.
 9. A screw as claimed in claim 7 wherein the inner hexagonal recess portion has six vertices and the nubs are positiOned in substantial axial alignment with alternate ones of the vertices, said nubs extending radially inwardly beyond the vertices of the inner recess, thereby requiring shearing of the nubs before the wrench can be advanced into the hexagonal recess. 